1. Field of Invention
The present invention relates generally to operation within communications networks such as, for example, hybrid network operation in which client devices can communicate using any one or more of several heterogeneous radio access technologies. More particularly, in one exemplary aspect, the present invention is directed to methods and apparatus for mitigating data transmission time-outs resultant from hybrid network operation.
2. Description of Related Technology
A cellular network operator provides mobile telecommunications services to the public via a network infrastructure of e.g., cellular base stations (BS), base station controllers, infrastructure nodes, etc. There are a wide variety of cellular network technologies, and historically cellular devices have been specialized for operation within a single cellular network. However, as cellular technologies have become increasingly commoditized, devices are now able to offer so-called “multimode” operation; i.e., a single device that is capable of operation on two or more cellular networks. Multimode operation allows a device to operate on any one of several network technologies, but does not enable operation on multiple network technologies simultaneously.
Incipient research is directed to so-called “hybrid” network operation. During hybrid network operation, the client device operates simultaneously among multiple distinct networks having different technologies. In one exemplary case, a hybrid device can support both: (i) Long Term Evolution (LTE) and (ii) Code Division Multiple Access 1X (CDMA 1X) networks; i.e., the device can maintain a simultaneous connection between a first LTE network and a second CDMA 1X network. For example, a LTE/CDMA 1X hybrid mobile device can conduct a voice call over the CDMA 1X network while the mobile device is in LTE mode. In another exemplary case, a hybrid device can support both: (i) CDMA 1X-EVDO (Evolution Data Optimized) and (ii) CDMA 1X networks.
Existing solutions for hybrid network operation rely on the client device to manage its own operation between networks. Specifically, the client device is responsible for maintaining its active connections to the various service networks; there are no required changes to existing network installations (i.e., hybrid network operation does not affect the legacy hardware and software of the network infrastructure). Client-centric hybrid operation has several benefits. For example, there is very little (if any) infrastructure cost for the network operator. Moreover, hardware costs can be incorporated into the price of consumer devices. Additionally, hybrid network operation will not affect existing legacy devices. Similarly, devices capable of hybrid operation are also capable of normal operation.
However, since existing solutions for hybrid network operation do not require the constituent networks to coordinate with one another, extant network equipment operation with client devices is less than optimal given the new demands placed on these client devices. For example, while a mobile device is attached to a first LTE network, it must periodically “tune out” the LTE network to perform CDMA 1X actions (such as decoding the Quick Paging Channel (QPCH) to determine if the device is being paged). If the mobile device is receiving data from a Transmission Control Protocol (TCP) server via the LTE network during the tune-out period, the TCP server will be unaware that the mobile device is tuned out, and will time-out its data transmission when it doesn't receive Acknowledgement Packets (ACKs) for the data that it had previously sent. Furthermore, TCP servers that back-off their data transmission drastically reduce the perceived throughput for the client device.
Consequently, improved methods and apparatus are needed for mitigating TCP level back-offs during these tune-out periods or other interruptions.